Recently, the development of an SSD (Solid State Drive), which is an alternative to an HDD (Hard Disk Drive), has been underway for use as a mass digital storage device. The SSD is configured with a nonvolatile semiconductor memory such as a NAND type flash memory, a controller therefor, and the like. The controller is configured with a semiconductor chip and a chip board, and the semiconductor chip is mounted on the chip board by wire bonding. The chip board as well as the flash memory is mounted on an SSD board.
In recent years, flip-chip mounting technology has been developed as an alternative to wire bonding, so that the semiconductor chip is mounted on the chip board using flip-chip technology. The flip-chip mounting bonds the semiconductor chip to the chip board by arranging very small metal protrusion (solder or the like) terminals called bumps on a front surface of a semiconductor chip, placing the semiconductor chip on the chip board so that the bumps come in contact with the chip board, and temporarily melting the bumps. An encapsulation portion (also referred to as “overmold”) formed from a resin material and provided on the wire-bonding mounting is often omitted in the flip-chip mounting. Use of flip-chip mounting is not limited to the semiconductor chip for the controller of the SSD and flip-chip mounting has been in widespread use in a broad range of fields.
A flip-chip mounting semiconductor device of related art is prone to ESD (Electro-Static Discharge) breakdown caused by static electricity. It is noted that the ESD breakdown occurs not only in the controller of the SSD but also in every semiconductor device using the flip-chip mounting.